1. Field of the Invention
The present invention relates to a grinding machine for grinding a workpiece such as a semiconductor wafer, a glass substrate, a ceramic substrate, etc. and a grinding method using the grinding machine.
2. Description of the Related Art
A semiconductor wafer, a glass substrate, a sapphire substrate, or a ceramic substrate such as SiC on which a plurality of devices such as ICs, LSIs or the like are formed is ground from a rear surface to a predetermined thickness. Thereafter, it is divided by a cutting machine such as a dicing machine or laser dicing machine into individual pieces, which are used in electronic devices such as cell phones, personal computers, etc. In general, a grinding wheel containing superabrasives such as diamond grindstones are widely used to grind the semiconductor wafer or the like. However, since the grinding by the grinding wheel is executed through fine brittle fracture, there arises a problem in that a ground surface causes a plurality of fine strains, which lowers bending strength of the workpiece.
To eliminate the problem, the ground surfaced of the workpiece after rough grinding is finish-ground and the finish-ground workpiece is subjected to finish processing such as polishing or etching to remove the strains generated by the grinding. As the finish grinding for a workpiece, a method is proposed for allowing gel-like slurry to flow out from fine pores of a porous pad and finish grinding the workpiece with superabrasives contained in the gel-like slurry. Incidentally, the gel-like slurry is a mixture of glue and superabrasives. If the porous pad gets wet, the gel-like slurry flows out from the porous pad to the upper surface of the workpiece. Thus, the workpiece is finish-ground with the superabrasives contained in the gel-like slurry.
A grinding machine combining the porous pad with gel-like slurry is effective in finish-grinding a workpiece. However, another grinding device is needed to rough-grind the workpiece with a rotatably driven grinding wheel. This is less preferable in view of economic efficiency.